This is a little thing.
An invalid "type" or "type body" does not show up in the browser when the My Invalid Objects option is selected.
They do show as 'INVALID' in the dba_(all_, user_)objects view.
I'm running:
PL/SQL Developer
Version 8.0.3.1510
01.60194 - 1 user license
Windows XP Professional 5.1 Build 2600 (Service Pack 3)
This didn't work in 8.0.0 either.